Blood culture bottles are superior to conventional media for vitreous culture

Endogenous Endophthalmitis - A Major Review

Endogenous endophthalmitis (EE) is an uncommon but potentially devastating ocular infection involving the inner layers of the eye. The global incidence of EE is on the rise. Common ocular signs and symptoms associated with EE include conjunctival injection, ocular pain, and reduced visual acuity. On clinical examination, a history of prior or coexisting systemic infections, symptoms (e.g., fever, malaise), and localizing features may be noted. Clinical diagnosis is often challenging, resulting in critical delays that contribute to a poor prognosis. Blood cultures and ocular fluid samples can aid in conforming causative pathogen(s), after which empirical antibiotic therapy, both systemic and intravitreal, should be instated. The use of steroids to suppress inflammation remains controversial. Surgical options include pars plana vitrectomy. Overall prognosis varies depending on host and pathogen factors, and early diagnosis and initiation of appropriate treatment are crucial.

Acute postoperative endophthalmitis: Microbiology from the laboratory to the bedside

Postoperative endophthalmitis is a dreaded complication of intraocular surgery. Acute presentations need prompt management and good knowledge of differential diagnoses. In the last 10 years, progress in direct microbial detection and identification from intraocular samples included the use of blood culture systems and, more recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, improving the rate of bacterial identification. Whatever the method used, diagnostic sensitivity is better for vitreous samples than for aqueous humor samples. Besides, molecular biology techniques have further improved the identification rate of infectious agents in intraocular samples. They also provide faster results compared to culture-based techniques. Quantitative real-time PCR (qPCR) can also determine the bacterial load in intraocular samples. Several studies have shown that intraocular bacterial loads in endophthalmitis patients are usually high, which helps differentiating infection from contamination. The prognostic value of qPCR remains to be validated. Whole genome DNA sequencing technologies facilitate direct and sequencing of single DNA molecules. They have the potential to increase the rate of microbiological identification. Some antibiotic resistance markers (e.g., methicillin resistance in staphylococci and vancomycin resistance in enterococci) may be detected earlier using molecular techniques (usually real-time PCR tests). Early determination of the involved microorganism and their antibiotic resistances can help establishing an earlier therapeutic strategy.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Ocular Infections

The variety and complexity of ocular infections have increased significantly in the last decade since the publication of Cumitech 13B, Laboratory Diagnosis of Ocular Infections (L. D. Gray, P. H. Gilligan, and W. C. Fowler, Cumitech 13B, Laboratory Diagnosis of Ocular Infections, 2010). The purpose of this practical guidance document is to review, for individuals working in clinical microbiology laboratories, current tools used in the laboratory diagnosis of ocular infections. This document begins by describing the complex, delicate anatomy of the eye, which often leads to limitations in specimen quantity, requiring a close working bond between laboratorians and ophthalmologists to ensure high-quality diagnostic care. Descriptions are provided of common ocular infections in developed nations and neglected ocular infections seen in developing nations. Subsequently, preanalytic, analytic, and postanalytic aspects of laboratory diagnosis and antimicrobial susceptibility testing are explored in depth.

Specific PCR and Quantitative Real-Time PCR in Ocular Samples from Acute and Delayed-Onset Postoperative Endophthalmitis

PURPOSE

Rapid identification of virulent pathogens is essential to strengthen the therapeutic strategy of acute endophthalmitis.

OBJECTIVES

This study sought to compare the contribution of a combination of polymerase chain reaction (PCR)-based tests to culture methods, in patients with postoperative endophthalmitis.

DESIGN

Prospective multicenter study diagnostic evaluation.

METHODS

Setting: university referral centers.

PARTICIPANTS

153 consecutive patients presenting with acute or delayed-onset postoperative endophthalmitis, between 2008 and 2015. There were a total of 284 aqueous humor (AH) and/or vitreous fluid (VF) samples. Outcomes and measurements: microbiological tests of intraocular samples included bacterial culturing of pediatric blood culture bottles; 16SrDNA amplification and sequencing (panbacterial PCR) for detection and identification of all bacterial species; real-time PCR (qPCR) assays targeting the femA or lytA gene for detection of Staphylococcus aureus (S. aureus) or Streptococcus pneumoniae (S. pneumoniae), respectively; and a qPCR assay targeting the tuf gene for detection and quantification of Staphylococcus epidermidis (S. epidermidis).

RESULTS

At the time of admission, the rate of detection of microorganisms by PCR-based tests was not significantly different than that by culturing (38% versus 30% in AH samples [n = 69]; 66% versus 63% in VF samples [n = 82], respectively). In contrast, after 1 intravitreal injection (IVI) of antibiotics, the identification rate by PCR-based tests was higher than that in VF by culturing (62% vs 48%, respectively; n = 94; P = 0.05). Bacteria were identified in 70% of patients, with a predominance of Gram-positive bacteria (93%). Specific qPCR tests targeting S. aureus and S. pneumoniae did not provide additional diagnoses but provided earlier results. The S. epidermidis load in vitreous at the time of patients' admission was higher in cases of final visual acuity (VA) of <20/40 (127,118 ± 125,848 DNA copies/mL) in patients with a VA of ≥20/40 (40350,000 ± 46,912 DNA copies/mL; P = 0.09). No significant changes in S. epidermidis load was found after one IVI.

CONCLUSIONS

Patients with acute or delayed-onset endophthalmitis should benefit from microbiological identification in vitreous samples by combined analysis using bacterial cultures in pediatric blood culture bottles and panbacterial PCR. The last test was more effective than cultures in vitreous samples collected after an IVI of antibiotics. The qPCR tests targeting S. aureus and S. pneumoniae gave earlier results than culture and panbacterial PCR but did not provide additional diagnoses. As for S. epidermidis infections, determination of bacterial load using the qPCR test targeting the tuf gene could help evaluation of the visual prognosis of patients. Its role in the follow-up of patients after antibiotic treatment needs further investigation.

Diagnostic value of pediatric blood culture bottles for acute postoperative endophthalmitis

OBJECTIVE

To report our experience using conventional culture methods (CM) and pediatric blood culture bottles (PBCBs) for vitreous sample culture of acute postoperative endophthalmitis.

METHODS

A retrospective study was conducted at the Department of Ophthalmology, Hospital das Clinicas, HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, BR, from January 2010 to December 2015, and it included 54 patients with clinically suspected acute postoperative endophthalmitis. Vitreous samples were obtained by vitreous tap or vitrectomy. Samples from January 2010 to December 2011 were cultivated in CM, whereas samples from January 2012 to December 2015 were inoculated in PBCBs. The measured outcome was the yield of positive cultures.

RESULTS

Twenty cases were included in the CM group, and 34 cases were included in the PBCB group. The yield of positive cultures in PBCBs (64.7%) was significantly higher than that in conventional CM (35%, p=0.034). Staphylococcus epidermidis and Streptococcus viridans were the two most commonly found agents.

CONCLUSION

PBCBs can be used successfully in clinically suspected endophthalmitis. The method showed a higher yield of positive cultures than the conventional method. This technique appears to have several advantages over the traditional method: it saves time, as only one medium needs to be inoculated; transportation to a laboratory is easier than in the traditional method, and there is no need to maintain a supply of fresh agar media. The use of PBCBs may be recommended as the primary method for microbiological diagnosis and is especially suitable for office settings and remote clinics.

Factors affecting visual outcomes after treatment of infectious endophthalmitis in northeastern Thailand

Objective

To determine factors affecting visual outcomes after treatment of infectious endophthalmitis during 2012-2016 at a large referral eye center in northeastern Thailand.

Patients and methods

Medical charts of patients with a diagnosis of infectious endophthalmitis including demographic data, types of endophthalmitis, causative organisms, methods of treatment, anatomical, and functional outcomes were retrospectively reviewed. Factors associated with improved visual outcomes were analyzed.

Results

Four hundred and eleven patients (417 eyes) were recruited for the study. The three most common types were post-traumatic (44.53%), post-operative (31.87%), and endogenous endophthalmitis (17.52%). Vitreous cultures revealed causative organisms in 41.25%. Most common Gram-positive organisms were coagulase-negative Staphylococcus 30% (36/120), Bacillus spp. 20% (24/120), and Streptococcus pneumoniae 18.33% (20/120). Most common Gram-negatives were Pseudomonas spp. 24.32% (9/37), Klebsiella spp. 24.32% (9/37), and Enterobacter spp. 16.21% (6/37). Methods of treatment were medical treatment (18.71%) and surgical treatment (81.29%), including pars plana vitrectomy with or without silicone oil tamponade (62.59%) and destructive surgery (18.71%). After treatment, visual improvement was noted in 44.6%, stable vision in 18.47%, and worse vision in 36.93%. Factors associated with improved visual outcomes were post-operative endophthalmitis (P<0.001), coagulase-negative Staphylococcus (P=0.003), and initial visual acuity before treatment of hand motion or better (P=0.017).

Conclusion

Most infectious endophthalmitis patients were post-traumatic, post-operative, and endogenous. The most common method of treatment was pars plana vitrectomy. Treatment could improve visual outcomes and at least stabilize the vision in 63.07%. Factors associated with improved visual outcomes were types of endophthalmitis, causative organisms, and initial visual acuity before treatment.

Diagnostic performance of blood culture bottles for vitreous culture compared to conventional microbiological cultures in patients with suspected endophthalmitis

The purpose of this investigation was to evaluate the performance of blood culture bottles in comparison to conventional microbiological culture techniques in detecting causative microorganisms of endophthalmitis and to determine their anti-infective susceptibility profiles. All consecutive cases with clinically suspected endophthalmitis in a university-based ophthalmology department between January 2009 and December 2016 were analysed in this retrospective comparative case series. Samples from 247 patients with suspected endophthalmitis underwent microbiological diagnostic work-up. All three culture methods were performed from 140 vitreous specimens. Vitreous fluid specimens were inoculated in blood culture bottles, aerobic and anaerobic broth solutions, and on solid media. Anti-infective susceptibility profiles were evaluated by semi-automated methods and/or gradient diffusion methods. Microorganisms were grown in 82 of 140 specimens for which all methods were performed (59%). Microorganisms were more frequently grown from blood culture bottles (55%) compared to broth solution (45%, p = 0.007) and solid media (33%, p < 0.0001). Considerable differences in the performance among culture media were detected for fungal pathogens. All grown fungi were detected by blood culture bottles (11 of 11, 100%). Broth solution recovered 64% and solid media 46% of grown fungi. No Gram-positive bacterium was resistant to vancomycin and all Gram-negative pathogens except for one isolate were susceptible to third-generation cephalosporins. In suspected endophthalmitis patients, blood culture bottles have a higher overall pathogen detection rate from vitreous fluid compared to conventional microbiological media, especially for fungi. The initial intravitreal antibiotic therapy with vancomycin plus third-generation cephalosporins appears to be an appropriate treatment approach for bacterial endophthalmitis.